CVE-2026-31786

Kernel memory disclosure via unterminated Xen build ID

Published Apr 30, 2026 · Updated Apr 30, 2026

Out-of-bounds read in Linux Kernel 4.13 and later allows local users in Xen domains to disclose kernel memory through a sysfs file. In buildid_show, sprintf treats the binary, non-NUL-terminated Xen build ID as a string and continues reading and copying beyond its bounds. Exposure requires access inside a Linux Xen domain; if the following 4 KiB lacks a NUL byte, copying crosses the sysfs buffer and corrupts kernel memory, causing a crash or privilege escalation.

CVSS severity7.8
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Linux Kernel 4.13 and later allows local users in Xen domains to disclose kernel memory through a sysfs file. In buildid_show, sprintf treats the binary, non-NUL-terminated Xen build ID as a string and continues reading and copying beyond its bounds. Exposure requires access inside a Linux Xen domain; if the following 4 KiB lacks a NUL byte, copying crosses the sysfs buffer and corrupts kernel memory, causing a crash or privilege escalation.

The record

CVE
CVE-2026-31786
Published
Apr 30, 2026
Updated
Apr 30, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-787, T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 30, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <4b4defd2fce3f966c25adabf46644a85558f1169
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <52cecff98bda2c51eed1c6ce9d21c5d6268fb19d
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8288d031a01dbacfde3fc643f7be3d23504de64d
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d5f59216650c51e5e3fcb7517c825bc8047f60ef
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e3af585e1728c917682b6a3de9a69b41fb9194d4
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f458ba102da97fafca106327086fc95f3fc764cb

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <4b4defd2fce3f966c25adabf46644a85558f1169; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <52cecff98bda2c51eed1c6ce9d21c5d6268fb19d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5c5ff7c7bd15bb536f44b10b3fb5b8408f344d0a; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8288d031a01dbacfde3fc643f7be3d23504de64d; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <d5f59216650c51e5e3fcb7517c825bc8047f60ef; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e3af585e1728c917682b6a3de9a69b41fb9194d4; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <f458ba102da97fafca106327086fc95f3fc764cb

Published CVSS scores

7.8kernel.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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